NEW ORLEANS – NEW ORLEANS (AP) — The oil spill in the Gulf of Mexico has already spewed plumes over ecologically sensitive reefs, part of a stalled marine sanctuary proposal that would restrict drilling in a large swath of the northern part of the vital waterway.

Marine scientists fear that two powerful Gulf currents will carry the oil to other reefs. The eastward flowing loop current could spread it about 450 miles to the Florida Keys, while the Louisiana coastal current could move the oil as far west as central Texas.

The depth of the gushing leaks and the use of more than 560,000 gallons of chemicals to disperse the oil, including unprecedented injections deep in the sea, have helped keep the crude beneath the sea surface. Marine scientists say diffusing and sinking the oil helps protect the surface species and the Gulf Coast shoreline but increases the chance of harming deep-sea reefs, which are seen as bellwethers for sea health.

"At first we had a lot of concern about surface animals like turtles, whales and dolphins," said Paul Montagna, a marine biologist at Texas A&M University Corpus Christi who studies Gulf reefs. "Now we're concerned about everything."

On Sunday, researchers said computer models show oil has already entered the loop current that could carry the toxic goo toward the Keys, the third-longest barrier reef in the world.

The oil is now over the western edge of a roughly 61-mile expanse of 300-to-500-foot-deep reef south of Louisiana known as the Pinnacles, about 25 miles north of where the Deepwater Horizon exploded April 20, killing 11 people and starting the spill that grows by the hour.

This sanctuary would have restricted fishing and oil drilling around the identified reef "islands." But the plan was put on hold after vehement objections from Republican lawmakers, fishermen and the oil industry.

Scientists have found undersea plumes of oil at the spill as much as 10 miles long, which are an unprecedented danger to the deep sea environment, said Samantha Joye, a professor of marine sciences at the University of Georgia.

These plumes are being eaten by microbes thousands of feet deep, which removes oxygen from the water.

"Deepwater coral are abundant on the sea floor in this part of the Gulf, and they need oxygen," said Joye, who was involved in the plume discovery. "Without it, they can't survive."

Experts say the well's depth and Friday's decision by the U.S. Environmental Protection Agency to allow BP to shoot massive amounts of dispersing chemicals deep underwater may help protect vital marshes and wetlands on the Gulf Coast. But the tradeoff may result in significant effects on more sea life.

Oil mixed with the chemical agent can disperse into the water more easily, rather than it staying on the surface, where it could bypass deeper banks like Pinnacles, said Edward Van Vleet, a chemical oceanography professor at the University of South Florida.

The downside is that it causes oil to sink, coating corals and other reef organisms and smothering them, he said.

When the dispersed oil is broken into smaller globules, he said they are more easily eaten by smaller reef organisms and can kill them or cause tumors or something else harmful.

Federal officials who oversee marine sanctuaries and fisheries say it's too early to tell how reefs and other important habitats may be damaged, said Dr. Jane Lubchenco, NOAA's undersecretary of commerce for oceans.

NOAA, which manages marine sanctuaries, is also responsible for estimating financial costs of the spill on the sea environment and fisheries. The Pinnacles is a significant habitat for sea life vital to commercial fisheries such as red snapper, crab and shrimp.

The creation of a sanctuary across hundreds of miles of the Gulf would not have blocked oil and gas exploration where the Deepwater Horizon exploded, said Montagna. However, he said it could have resulted in stricter environmental regulation for reefs closest to the spill site, and likely less drilling.

"So you can imagine these animals that make a living on rocks, filtering food out of the water, and the dispersants come along and sink the oil; it's a big concern," Montagna said.

The area also is breeding ground for sperm whales and bluefin tuna, species not doing well, he said.

Studies published in a 2005 National Academy of Sciences report show that oil mixed with dispersants damaged certain corals' reproduction and deformed their larvae. The study concluded the federal government needed to study more before using massive amounts of dispersants.

Reefs are made up of living creatures that excrete a hard calcium carbonate exoskeleton.

Depending on the oil exposure, they can be smothered by the pollutants or become more susceptible to bleaching, which hinders reproduction and growth. While the warm temperatures of Florida could speed the recovery of damaged reefs there, some problems could be seen for a decade or more. In the deeper reefs in colder water closer to the spill, the damage could last even longer.

As the spill increases, the oil oozes toward other reefs that stretch from the blowout site eastward to the Florida Keys National Marine Sanctuary.

The Keys exist in relatively shallow water, so the potential exposure to the oil is higher than for deeper reefs, though BP PLC officials say the oil would be more diffused after having broken down during its travel over hundreds of miles.

This week, researchers from USF and the Florida Department of Environmental Protection are heading to the loop current to get a "chemical fingerprint" of any oil they find to confirm it is from the leaking well.

"We don't expect the loop current to carry oil onto beaches," William Hogarth, dean of the University of South Florida's College of Marine Science, said. "But we do have a great concern for the Keys."

If oil reaches the Keys, it could threaten one of the country's greatest underwater natural resources as well as its tourism industry.

Locals throughout the ribbon of islands not only relish their ties to the water but rely on it to help bring in 2 million visitors each year.

"They're not going to come if our beaches are tarred and our mangroves have died and it's a polluted dump," said Millard McCleary, program director of the Key West-based Reef Relief. "They'll go to the Bahamas or the Caymans or they'll go to Mexico."